Is it possible to upgrade a 98 engine (1970 seigorni (just the road version unfortunately) apparently) to 124cc ?
I know the early series had a lot in common and it looks as if you should be be able to swap in a 124 cylinder, piston and head (ignoring balance factor). I know about the 13.5 and 15 piston pin variants but until I lift the cylinder I don't know which this will be. Is it simply a case of the later ones being 15, and if so from which year? The stroke is the same and piston height as far as I can tell.

Would the 98 cylinder stand boring out to take a 124 piston but use a 98 head? Given it's a hemi head design presumably not.

I know 124s must have had a different head as the valves are bigger.

This 98 has a cast iron cylinder not alloy/iron sleeve so I'm wondering if someone may have put a 'lesser' or earlier engine in (number starts with 001). Though it has a Dellorto ME18BS carb not the 16 that it seems the early 98s (1962 at least) used.

It needs a rebore anyway so just exploring options if it is already beyond maximum usual oversize for a 98.